In recent years, with organic electroluminescent devices (hereinafter referred to as ‘organic EL devices’), a method has been proposed in which an organic EL device is combined with color-converting layers obtained by processing fluorescent color-converting materials into the form of a film, whereby colors different to the color emitted by the EL device are obtained (see, for example, Japanese Patent Application Laid-open No. 3-152879 and Japanese Patent Application Laid-open No. 5-258860).
Such a color conversion method has the following advantages as a method for obtaining a desired spectrum when constructing a full-color display: (1) compared with a three primary color emission method, there are fewer restraints on the emitted color, and hence a light emitter constitution with higher efficiency and higher brightness can be used, and as a result it is easy to improve the efficiency and make the patterning more detailed; and (2) compared with a white light emitter plus color filter method, less light is lost through the filters, and hence it is easier to increase the efficiency.
With the color conversion method using an organic light emitter that emits blue light, the blue light is subjected to wavelength conversion into green light and red light (see, for example, Japanese Patent Application Laid-open No. 3-152879, Japanese Patent Application Laid-open No. 8-286033, and Japanese Patent Application Laid-open No. 9-208944). If such emitted light wavelength converting films containing fluorescent colorants are patterned with high detail, then a full-color luminescent-type display can be constructed even if low-energy radiation such as near ultraviolet light or visible light from a light emitter is used.
Materials that emit fluorescence from visible light are generally used as the fluorescent color-converting materials used in the color conversion method. However, such materials also react to light other than that from the organic EL device, and hence the ability to see whether or not the light emitters (pixels) are lit is reduced under illumination with, for example, a fluorescent lamp or sunlight. That is, under an ordinary usage environment, the color-converting layers will be excited even when the light emitters are not lit, and hence the brightness ratio between when a light emitter is lit and not lit will inevitably drop, and thus a problem will arise in that the contrast ratio in bright places will drop, and hence the display quality will drop.
Attempts have been made to ameliorate this problem by inserting a contrast-improving layer, i.e. a color filter layer, that block the infiltration of light into the color-converting layers from the outside (see, for example, Japanese Patent No. 2838064 and Japanese Patent Application Laid-open No. 2000-3786). This color filter layer is a filter layer that transmits only the color of the light emitted by the color-converting layers. However, even if such a constitution is adopted, there is light that passes through the color filter layer for improving the contrast and the color-converting layers and reaches lower metal electrodes, is reflected at the surface of the metal electrodes, and is led out to the outside as reflected light; the problem that this reflected light causes a worsening of the contrast ratio as before has not been resolved.